The invention refers to a device for protecting against the unauthorized use of software.
State-of-the-art: in the SAM copy protection system from Comprotec, encrypted, secret programs of a protected PC application are transmitted to a dongle connected to the PC. The dongle contains a device for decrypting and executing the program. During execution of the program, unencrypted data are exchanged with the protected application. The protected application only works properly if the data exchanged are without errors. This is only possible if the dongle is connected to the PC. The dongle is usually distributed together with the protected application. Since the dongle is very difficult or even impossible to reproduce without knowledge of the secret technical details and the programs run on the dongle are kept secret, unauthorized use of the application is prevented. The secret programs can also read and write to a persistent memory on the dongle. This enables, for example, license information to be transmitted to the dongle without this procedure being manipulated externally.
The disadvantage of this copy protection device consists thereof that the copy protection manufacturer cannot change the processor type on the dongle without requiring considerable changes to the protected applications and the secret program code. Moreover, the application provider is committed to using a dongle from a particular provider of copy protection. The use of dongles from other copy protection providers is generally not possible without changing the application if these use other types of processors. Another disadvantage is that the copy protection provider can only use processors that enable the program code to be read from RAM. Since the programs should be replaceable, reading from a ROM or EPROM is not an option. Using smart card controllers which meet high security standards is generally not possible, since these generally only run permanently stored program code. Furthermore, the creation of a standard for license transactions is not possible, if providers of copy protection use various processor types with diverse instruction sets.